1. Field of the Invention
The present invention relates to a seatbelt device, and more particularly, to a seatbelt device comprising an electrical actuator.
2. Description of Related Technology
In a conventional seatbelt device, if there is a possibility of a collision, the seatbelt (webbing) is wound up by an electrical actuator before the collision, thereby lightly restraining the occupant, and when there is no longer a possibility of collision, the seatbelt is returned to the state before collision. In the event of a collision, the restraining force is increased by a pre-tensioner, thereby reliably protecting the occupant (see, for example, Japanese Patent Application Publication No. 2005-88838.)
Furthermore, in Japanese Patent Application Publication No. 2005-88838, a torque limiter mechanism is provided in a power transmission mechanism which transmits motive power from a motor (electrical actuator) to a spindle, in order to restrict the transmission of excessive torque by the motor when the motor is driven to perform a wind-up operation.
Therefore, the operational torque of the torque limiter mechanism is set lower than the gear strength and higher than the winding force of the motor. However, if the motor is operated from a state including slack, for example, and the seatbelt is pulled out violently, or the winding action is locked, then a winding force equal to or greater than the setting may be generated momentarily due to the inertia force of the gearbox itself, including the motor, and hence the torque limiter mechanism may operate. Operation of this kind can be resolved by increasing the operational torque overall, but this affects the operating characteristics of the torque limiter mechanism.